Turbine blades are the primary elements of wind turbines for converting wind energy into electrical energy. The blades have the cross-sectional profile of an airfoil such that, during operation, air flows over the blade producing a pressure difference between the sides. Consequently, a lift force, which is directed from a pressure side towards a suction side, acts on the blade. The lift force generates torque on the main rotor shaft, which is geared to a generator for producing electricity.
The turbine blades typically consist of an upper (suction side) shell and a lower (pressure side) shell that are bonded together at bond lines along the trailing and leading edges of the blade. The bond lines are generally formed by applying a suitable bonding paste or compound along the bond line with a minimum designed bond width between the shell members. These bonding lines, particularly at the trailing edge of the blade, are a critical design constraint of the blades. A significant number of turbine blade field failures are bond line related, with trailing edge failures being the most common. Separation of the bond line along the trailing edge of an operational turbine blade can result in a catastrophic failure and damage to the wind turbine.
In addition, the trailing edge bonding process is a challenging and time consuming task. Application of the bond paste to achieve the required bonding thickness and width is difficult. Post bond trimming of the trailing edge to remove excess bond paste, trim reinforcement material, and so forth, is a time consuming and expensive finishing operation. Even after the trimming process, it is often necessary to perform subsequent trailing edge repairs/modifications before the blade is field-ready.
Conventional trailing edge bond configurations are also highly susceptible to erosion in the field, which results in costly and expensive field repairs.
U.S. Patent Application Pub. No. 2007/0025858 proposes to provide a trailing edge cap intended to be placed over the designed trailing edge of a wind turbine blade in order to reduce noise generated at the trailing edge. The cap has a configuration so as to extend well past the original trailing edge of the blade and to define a reduced trailing edge thickness as compared to the original trailing edge. The cap is flexible and is designed to conform to a variety of differently sized and shaped turbine blades. Although this trailing edge cap may provide reduced noise benefits, it does not address the trailing edge structural bonding issues discussed above.
Accordingly, the industry would benefit from an improved bond configuration that is cost effective, time efficient, and produces an improved structural bond, particularly along the trailing edge of the wind turbine blade.